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Finding the scale waterline for a new model ship can be a bit of a challenge. Here is one method that will give you a close approximation of the waterline for almost any ship of any particular size. Instead of the traditional putting the scale amount of weight in the ship and floating it in a bathtub, you will be filling the ship itself with water to its scale weight.

Gather your measurements. You need the

  • weight of the empty model ship (from your own scale)
  • scale weight of the ship (see below), and (optional) +10%, -10%, and -20% of this scale weight
  • scale width of the ship (calculated from a reference book)
  • amount of water to add to the ship (see below)

For 1:144 scale models, the scale weight of the ship is the full displacement in long tons divided by 1333 to get the weight in pounds. MWCI also has an extensive ship list with the scale weights at http://mwci.org/shiplist.shtml . For other scales, use the following calculation: scale weight = (Full displacement weight in long tons)*2240/(scale^3).

To determine the amount of water to add to the ship, subtract the weight of the empty ship from the scale weight of the ship. That is the amount of water, in pounds, you need to add to the ship. Each pound is about two cups of water (one gallon of water is 16 cups, and weighs about 8.345 pounds).

You need a completely uncut hull, as we will be filling it with water.You will also need a marker or a pencil (but not a grease pencil), and shims or a way to keep the hull level if it is not a flat-bottomed hull.

  1. Use packaging tape to tape the hull width to the scale width, so the hull does not expand when you fill it with water.
  2. Find a level slab of concrete for your hull. At the top of the hull, make sure that it is level from side to side. If it is a small ship like a cruiser that does not have a flat bottom, use shims to keep the hull upright and level.
  3. Add the correct amount of water (from your calculations above) to the hull.
  4. Mark the water level in the fore, aft, and midships of the hull.
  5. If desired, change amount of water to +10%, -10%, and -20% of scale weight and mark the water level.

These markings will be very close to the desired water line when the ship is finished, but will be slightly low because the density of the fiberglass is higher than the density of the water. On an Iowa hull, the different in that water level appears to be about the difference of one pound of water added.

An Iowa class battleship has a scale weight of 44.5 pounds and the dry, uncut hull weighs about 4.875 pounds. After taping across the sides to keep the beam width at 9 inches, add 39.625 pounds of water (4 gallons and 3 quarts). The water level will be very close to the desired water line once the ship is finished.

This method of finding the waterline will not work on ships whose keels are not level with the waterline. Some destroyers are like this and there are probably others. Most of the larger ships should be OK as their keels were built on a flat and level surface.

General Construction Tips
(Original Article by Phil Sensibaugh, edited by Bill Pickl)

Begin with the end in mind. Install the systems in the proper order. Many skippers end up installing the hardware several times because they get ahead of themselves. It’s common to complete the hull and install the drive motors, only to discover that the stern cannon won’t fit in the hull because the motors are in the wrong position. The rules mandate that the cannon must be located in the same position as on the real ship. Other systems, to include the motors may be installed anywhere in the hull, so the cannon must be installed first.

Think small and think light. You can always add more weight if needed and if added late in the building cycle the weight can be placed where it is needed to accommodate balance. Keep hardware close together – pack it in, but keep it modular so it can be removed easily for maintenance. Open spaces inside your hull don’t hurt anything and allow for future flexibility. Keep hardware in the smallest space possible. Don’t spread it out in the hull just because it looks like you have extra room. There is no such thing as extra room in an RC combat warship.

Think about maintenance when building your ship. Make all systems modular and removable and never install any component of you ship hardware permanently in the hull. For instance, don’t glue the cannon down to the bottom of the hull thinking that you’re saving time and likewise with other hardware. Sooner or later you will have to remove it for maintenance. Think ahead. Think simple. Make repairs easy and timely.

Build modular systems to make life simple. A warship has many operating systems to include motors and drive gear, pump, weapons, flotation, electrical and pneumatic plumbing, to name the predominate systems. Such a maze of hardware, electrical wiring, and plumbing can baffle even an experienced modeler on first glance. To keep it all manageable just consider each system as a stand-alone item, and build it accordingly. Use quick disconnect fittings on CO2 lines and connectors on electrical wiring. When you look at your ship don’t view it as a maze of components, but as a group of independent systems. Remember that each system by itself is really pretty simple and with some common sense you can figure it out, but if you build your boat so systems can be isolated trouble shooting becomes that much easier. This means that during construction you must avoid “daisy chaining” systems together and build each system as a stand-alone item. Bundle the wires together and put a cable tie around them to make it look neat and take up less space. Cut off any excess wiring (shorten wires as needed), but allow a couple of inches of extra wire for future service. Do likewise with the pneumatic plumbing. Following these steps will make your boat a lot easier to work on. For instance, if a motor fails and is isolated the rest of your systems will still be operational. Whereas the opposite is having your whole system go down without any idea of where the problem occurred would take a long time to diagnose and fix.

Keep weight low in the boat. If you have ever stood up in a canoe or watched what happens when someone does you will appreciate this advice. The key to a stable weapons platform is keep all possible weight below the waterline and minimizing the weight of anything located above the waterline. Lie batteries flat on the bottom of the hull keeping total mass of batteries below the waterline. Mount cannon low in the hull and extend barrel riser tubes to proper barrel height, don’t raise the whole cannon. A low center of balance is imperative to achieve ship stability.

(Original Article by Phil Sensibaugh, edited by Bill Pickl and Strike Models) Note: this is one section of a comprehensive model warship construction manual originally published on the BDE/RC website. This section is applicable to both Big Gun and Fast Gun combat.

This article does not discuss how to make the packing tubes or prop shafts. That is a topic of an article in the Drive Train section of this manual. Before you get started locate the position of your rear cannons in your hull set them inside and determine approximately where you want to locate your motors and where you want the packing tubes to end. This will eliminate the need for modification of your prop stuffing tubes later on when you begin installing the hardware into your boat.

Installing prop shafts and packing tubes is far less difficult than most builders make it. An important thing to remember is not to be overly critical when cutting a hole(s) in you hull for the prop shafts. The holes will probably be in the wrong place no matter how much time you spend thinking about anyway, so just cut them. Oversize holes are easier to fill later.

If you have a wood frame hull you can install the prop shaft packing tubes before or after the hull is sheeted and fiberglassed. Due to the nature of the Iowa prop and skeg arrangement I chose to install them first. Just remember that it is very important to determine how and where your cannon will mount in the hull before installing the packing tubes, otherwise you will surely install them in the wrong place.

The upper photos show how the packing tubes were aligned parallel to one another and level, glued to a wood dowel that was carefully measured and marked. If you are using a fiberglass hull and brass stand-off supports for the ends of your packing tubes then use the dremel to cut a slot for your brass stand-off support near the end of the packing tube. Slide the brass support into the slot as you  tilt your packing tube in place and glue to the wood dowel. Ribs were ground away as needed to allow the tubes to lie level with one another and fit in place at a slight downward angle. The tubes were secured in place with epoxy putty, which also reinforced the ribs that were ground down substantially.

If you are using the brass stand-off support for the end of your prop shaft and have not yet sheeted the bottom of your wood hull then glue cross support between ribs so that you have something to glue the supports to.

Wood sheeting was installed around the tubes and stand-offs (editors note: the above article on wood hull construction suggests the use of hardwood strips instead of balsa wood sheeting), but a small space was left open around the rib. This hole was filled with epoxy putty, which is a great water seal and also gives a nice appearance to the hull and looks like the packing boxes on real ships.

The third photo shows how the over size holes cut into a fiberglass hull were filled with epoxy putty. It also shows the extreme angle on the coupling for the motors that was required to allow the cannon to fit between the motors. As it turns out, the center motor was still in the way of the stern cannon and had to be removed and installed “backwards” above the packing tube using an o-ring drive or gear drive. The motors are installed by attaching small sections of brass tube to the hull with epoxy, then slipping plastic wire ties through the brass and around the motors. This is a system that has proven to work very well.

The bottom photo shows the running gear of the Scharnhorst, which is one of the most difficult ship hulls to outfit. Three props and two rudders fit into a very small space, but it can be done.

(Original article by Phil Sensibaugh, edited by Bill Pickl and Strike Models)
This material was originally published on the BDE/RC website as an instruction manual for getting started in Big Gun Model Warship Combat. This chapter is applicable to both Big Gun and Fast Gun formats. View the manual homepage.

Have you ever wondered why some ships settle fairly evenly in the water when they flood internally while others take on a severe list? The reason is most likely inadequate water channeling. Water, being a liquid will seek out the lowest point of the ship and move in that direction. It also follows the laws of physics and reacts whenever the ship moves. If the ship turns right the water will move to the left, and visa-versa. Also, when the ship moves forward the water will run towards the back. This is why nearly all ships sink by their stern, rather than bow first. In fact, of the several dozen of ships I have seen sink I have never seen one sink bow first. Although sinking bow first would be a good feature since this has the potential to save the rudders and props from damage when the ship hits the bottom, or is recovered. I say “potential” damage because after six years of battling the MBG (Midwest Battle Group) has yet to see any props or rudders damaged by sinking, but it could happen.

I’ve developed effective water channels with the past nine ships I’ve constructed and the method I have come to like the best is the foam filled water channel. I like this method since I’ve found it the easiest to accomplish. To make the water channel I first installed two wood stringers down the center of the hull and separated by about 2.75 inches. The stringers should be 1/4″ x 1/4″ hardwood. These stringers also serve to add some strength since the bottom plate of this ship (wood construction) was made up of seven sections to prevent warping. Next grind down the portion of rib that is glued to the base plate so that it will form a sloped line going from the 1/2″ tall height of the rib to the center 1/4″ tall strip (editor’s note: its easier to layout the rib patterns with this slope in mind and save the grinding). In addition to the channel down the middle you may want to leave an open section sized for your batteries so you can keep this large piece of weight low in your hull. Make this battery space an 1″ longer than the battery you intend to use and typically centered amidships with the batteries placed out towards the side of the ship to allow for a CO2 tank between them.

If you are putting a channel in a fiberglass hull your job is a bit easier. After attaching the sides of your channel to the bottom of the hull you will need to add a stringer that goes from the edge of the water channel out to the side of the hull about every 4″ along the length of the hull. You will need to cut a slope on them such that they are 1/4″ tall on the water channel edge and 1/2″ tall on the end near the side of the hull. I recommend you work with 3/4″ by 1/4″ hardwood strips. Measure off the length of stringer that will fit in the section of hull you are currently working on and measure in 1/4″ on opposite ends of the rectangle and draw a diagonal line between the two. The result should be a matched pair of wedges that are the same length and 1/4″ tall on one end and 1/2″ tall on the other. Make your diagonal cut first down the center then make the cross cut. Glue these two pieces to the hull and you’ve created your own “rib” stringers and you are ready for the next step.

I then installed a piece of balsa over the ribs between the water channel stringer and the side ribs of the ship as shown in the accompanying photos. Since the part of the ribs that were glued to the hull keel plate were sloped towards the center this allows any water coming in through holes on the sides to run into the water channel and towards the pump. Then I drilled a hole in the balsa sheet between each rib and using a can of “Great Stuff” minimal expanding spray foam I filled each rib section with the foam. My first attempt at this several years ago the foam simply forced off the balsa, cracking it to pieces. The accompanying photo shows how even minimum expanding foam still expands greatly (there are some new very minimal expansion foams on the market get some and experiment). The spaces between the ribs were only 2/3 filled!

Using a small blade on my pocketknife I cut away the excess foam, which was quite easily accomplished, then sheeted over it with more 1/16″ balsa sheet. Be sure to use epoxy glue for this since CA glue will melt foam, as will fiberglass resin. When the whole hull was sheeted on the inside so I couldn’t see foam anywhere I put a thin coat of “SolarEZ” UV cured polymer resin over the inside of the ship. This product won’t hurt the foam and cures more predictably than conventional fiberglass. The trick is sunlight must be able to reach it in order to cure the resin.

Now that the water channel is installed you should have a ship that will settle level as it takes on water.

Original Article by Phil Sensibaugh. Edited by Bill Pickl and Strike Models. Note: this is one section of a comprehensive model warship construction manual originally published on the BDE/RC website. This section is applicable to both Big Gun and Fast Gun combat.

Strike Models Note: We advise talking to someone who has already built a ship from scratch, as they can be a big help. Also, please check your club’s rules regarding rib spacing and allowed penetrable area and use those rules over what we included here. A very detailed instructional forum thread about scratch building a SMS Pommern (a predreadnought) is being chronicled on the RC Naval Combat website.

I have often been asked what I felt was the best way to construct a hull “from scratch.”  I’ve seen several methods used with some methods working better than others, yet still I’m not sure if there is one best method. I believe if the hull doesn’t warp, isn’t overly heavy, and floats somewhat level when empty (no major list) it’s a good hull. I suppose I should add in one other criterion as well, it shouldn’t leak. This article will cover: Making a Pattern Set, Selecting Construction Material, and Assembly.

The premise for developing patterns sets for a scratch built hull is that the ship will be built on a flat bottom plate with ribs, bow and stern keels being glued in vertically all topped by a caprail. Strike Models offers several such pattern sets ready for cutting and assembly, but this section will cover the basics of developing your own pattern sets should they not be commercially available. Using the baseplate method of building is recommended otherwise you will have to set the ribs on a keel, which requires jigs and fixtures to achieve good results and the keel will be in the way later anyway. Flat bottom boats are much easier to build, but don’t confuse a flat bottom with a shoebox shaped hull. The sides will still be rounded, as will most of the hull below the waterline. Real warships are generally flat on the bottom as can be verified by your ship plans.

First, obtain a set of plans for your ship. The greater the detail shown on the plans the better, but don’t be surprised if the detail is lacking. Often a set of plans consists of a top and side view of the hull and superstructure and a drawing of the ribs at a few stations along the hull, but this will suffice. [If you contact Strike Models, we can tell you the level of detail for each particular plan we sell.] The plans usually don’t provide enough ribs for the required spacing (1, 2, or 3 inches) so you will need to draw additional ribs. Look at the overhead view of the provided rib locations. Next decide the spacing you will use. Use of 1/4″ wide ribs on 2″ spacing is the most common selection, but for large ships 3/8″ wide ribs on 3″ spacing is also used (Big Gun only, and even that is dependent upon your club. Fast Gun has significantly different rules). With your spacing selected you will need to draw lines on your overhead view where you need to add ribs. You will often need to add one and sometimes up to three ribs in between those provided by the plan set. What I recommend is making a copy of the original ribs and hand sketching the correct number of ribs in-between the provided rib profiles.  Just eyeball even spacing for the number of ribs you are adding. Be sure to reduce the overall rib width by the thickness of the balsa sheeting on the hull, and the overall height by the thickness of the caprail and bottom plate. Do this by drawing a line below (3/8″ for plastic 1/4″ for wood) the top of the rib for your new rib top and a line 1/8″ above the bottom of the boat. Also draw reference lines for  the water line and a line one inch below the water line across the ribs. Note that often only half of the ribs are drawn, so you’ll have to draw the mirror image of each rib the best you can including the added ribs. When I do so I use a light tracing paper that you can see through easily, draw half the rib, fold the paper in half then copy the other half of the rib off the first half. Another method is to make a copy of the ribs then trace them on the back of the paper copy, thus making a mirror image. When you have a complete set of full width ribs COPY all of your work and save the original drawings. Make one copy for each of the ribs.

For each rib highlight the correct exterior hull line the top and bottom (remember to follow the lines that allow for the bottom plate and the caprail). Also on the exterior line mark an 1/8″ deep notch on each side of the rib at a point starting one inch below the waterline and extending to the bottom of the rib. Hardwood stringers will be installed here later on to help form the impenetrable area of you hull. On some of the wider ribs you will not need a rib that goes completely across the bottom of the hull. If the flat spot in the rib is more than 4.5″ wide then you will draw a left and right piece. You may wish to read the section on water channels at this point so you can design your rib patterns to accommodate water channeling. The water channel will be 2.75″ wide so measure 1-5/8″ inches left and right of the center point on the flat bottom of the rib profile to allow for the water channel stringer. Make these marks 1/4″ high. At the outer edge of the flat spot measure 1/2″ up and draw a diagonal from that point to the top of the 1/4″ tall line that marked the top of the innermost edge of the rib’s bottom.  Next sketch in a line about 1/2″ in from the exterior hull line to complete the inside edge of your rib. You will want to mark the location of the prop shafts on the appropriate rib patterns, usually the rib just forward of the propeller and the two ribs forward of where the shaft enters the hull. For the rib just forward of the prop you will need to draw in braces to support a circle big enough to drill the hole through for the prop packing tube.

The next items to make patterns for are the bow and stern keel plates, the caprail, and the baseplate. Start with the base plate. Take your rib patterns and measure the “flat” width at the bottom of the ribs. For all ribs with a flat spot at least 3/8″ wide and that touch the bottom plate transfer those measurements over to a sheet of paper. Remember to also measure the distance from the bow to each rib from your overhead view and transfer these to your base plate pattern. You should end up with a center line with rib locations marked and each rib location will have a perpendicular line centered on the center line that represents the width of the flat bottom of the rib. To complete the base plate pattern just connect the outer edge of the rib lines. Next to make the bow and stern keels trace the side view of the bow and stern profile. Measure in about 1/2″ in from the profile and make another line. You will want to make the keels long enough to overlap the base plate at least 3 inches. Remember to make a 1/8″ allowance for the base plate. Also note that a few of the forward and stern ribs will not attach to the base plate but to either the bow or stern keel. These rib drawings should be modified with a notch to slide onto the keel and remember to keep the depth of the ribs all the way to the bottom of the keel, since they do not rest on the bottom plate. Some ribs that are on the base plate may need to have a notch added to their pattern to allow for the overlapping bow and stern keels. To make a pattern for the caprail trace the outer edge of the ships deck from the overhead view (please note that some odd ships are wider at the waterline then at the deck or caprail level). Draw a second line a half inch in to complete the pattern. You may also wish to design in some cross braces into the caprail pattern. These help the ship maintain its desired width and to reinforce the hull should it ever need to be pulled from the water with 100 pounds of water in it!  Make copies of all these patterns as well.

You are now ready to select the material for your scratch built hull. Some people prefer 5-layer plywood, while the MBG (Midwest Battle Group) now has three plastic hulled ships. The plastic is foamed PVC and can be obtained in various thickness’ from an industrial plastics supplier. Foamed PVC enjoys the advantage of being lightweight and strong, easily cut and glued with CA glue, is inherently waterproof and will not warp or rot. If you do chose to use plywood the following precautions must be followed. Cut your caprail and base plate patterns into pieces between 12 to 18 inches to prevent the wood from warping. Cuts should be made at a rib location.

Glue the copies of the tracings to plywood using Elmer’s glue, or some other water-soluble glue, then saw them out slightly oversize. Use material of the appropriate thickness corresponding to the rib spacing of your pattern. For the base plate use 1/8″ and for the caprail use 3/8″ for plastic and 1/4″ for wood. Next sand the pieces to the correct size. Finally remove the paper from the wood or plastic with warm soapy water, then dry the parts well. Don’t be concerned if the wood parts warp somewhat. If the wood is going to warp, now is the time to find out. If warping of the longest sections of the cap rail or bottom plate occurs just cut them into shorter sections, preferably at rib location. A little warp won’t hurt anything at this stage of construction. We’ll fix it later.

If you chose wood as your material you will need to glue sections of the caprail and base plate together, end to end on a flat surface and while laying over a tracing of the plans. This will ensure the sections have the proper curve to match the hull. Likewise, with the bottom sections of the hull. Epoxy glue works well for this purpose, but CA is too brittle and will not work well. Don’t be concerned if they look weak lying there. We’ll strengthen them plenty later on. When the glue dries, lay these sections over the plans and mark the positions where the ribs will attach. Now attach the ribs to the base plate with one or two drops of CA glue. Don’t glue them too well right now since you may need to remove the later if something doesn’t line up right. Next, look at the hull from the end and visually verify that the ribs are symmetrical on both sides of the hull. There’s a photo of this step later in this article. Now attach the cap rail to the top of the ribs. Some of the ribs may not line up with the cap rail well, but don’t force the caprail down, or up to the ribs. Trim or file the ribs as needed to line up with the level caprail. Note the word level!  There are photos accompanying this article that will help you visualize how the hull will go together.

Once the hull is glued (tacked) together in this state it will still be very frail so handle with care, but don’t panic yet. Next will come the strengthening. Place the hull on a flat surface and inspect carefully to see if the hull has developed a warp. If so just break a few glue joints to relieve the pressure, then glue them again. You may also need to make a few cuts through the caprail or base plate to relieve pressure to eliminate the warp. Make as many cuts as needed to get the warp out. Once again, don’t worry, you’re not weakening your hull permanently.

Now the strengthening of the hull begins. For wood hulls install hardwood (spruce) strips the thickness of the balsa sheeting allowed (1/16 to 1/8 inch). These stringers will be 3/8″ wide. This width will allow the strip to overlap the ribs by 1/8″, since the wood caprail is only 1/4″ thick. These strips are installed around the caprail on the inside and outside of the hull. You can cut the stringers into shorter sections, but make sure the joints are staggered and the inside stringer joint does not occur on the same rib as the outside stringer.  Again installing them on the bow and the stern is the trickiest part to accomplish. To allow the hardwood to bend around the curved areas cut notches about 2/3 though the wood stringer about every 1/4″ in the inside the side that will be next to the hull, then bend the stringer until it cracks at the notches. I use the Dremel tool and cut off wheel to make the notches.

Next, install 1/8″ by 1/8″ stringers (preferably spruce) in the notched portion of the ribs that starts 1″ below the waterline and extends down to the base plate. The stringers do not need to butt up closely together, as you will cover this portion of the hull with fiberglass. Assuming your hull is still true and not warped go back and brush epoxy glue on all wood joints that were tacked with CA glue. For plastic joints a bead of CA glue along both sides of the joint will permanently bond the plastic parts together. Invert the hull and brush the epoxy inside the sandwich formed by the two hardwood stringers and the caprail. Wait for the epoxy to cure and you’ll see that this step will have strengthened your hull dramatically.

Now the hull should look nearly complete save for the side skin. Sand all outer surfaces of the hull so that they are smooth in preparation for fiberglassing the bottom. Next, place the hull top down on a flat surface and add spacer beneath it to allow it to lay flat and be supported. If the hull has taken on any warp you must get the warp out at this time. Check the hull closely for warping. Don’t be afraid to cut the hull in two and glue it back together if needed to correct a warp. Now is the best time to fix them.

Fiberglass resin has quite an aroma (it stinks) so find an area to work with good ventilation. Cover the work area with a sheet of plastic. Now make a stand to hold the hull off the work so it can lay inverted (upside down) and be stable. The stand must hold the entire hull (for wood only) off the work area to include the bow and cap rail since we’ll be glassing them also.

Next, cut the lightweight fiberglass cloth in to small sections about 12″ square, or whatever size or shape is needed to cover the hull. Small sections of cloth are easier to work with and to keep air pockets out of. At this point I would recommend purchasing an ultra violet cured resin sold by SolarEZ. This stuff is just like epoxy resin with the added bonus of only hardening when exposed to about 30 minutes of strong sunlight. If you keep the windows covered in your shop you will be able to work at your own pace rather than at the pace of the setting time of normal resin. Apply a thin coat of resin to the hull bottom and sides down to the penetrable area, then lay on a section of fiberglass cloth and apply another thin coat of resin over the cloth. Repeat this procedure to apply the next section of cloth, overlapping the previous section by 1/4″ to 1/2″. Continue laying cloth until all the wood stringers on the bottom of the hull are covered with fiberglass cloth and resin. Remember a thin coat of resin is all that is desired. Applying more resin just makes a mess and increases the amount of sanding needed. Sanding fiberglass is no fun. The cloth will try to “slip” across the wood as you brush resin on, so reverse directions of your brush strokes regularly and use a gloved hand to push or pull the cloth. As you are progressing smooth out the cloth, working out all air pockets and wrinkles. Cut the cloth with an Exacto knife to let the air escape if necessary and overlap the cloth at the cut then smooth it down. This will be especially necessary in the bow and stern where there are a lot of curves. Continue this effort until the hull is covered, bow to stern, to include the solid bow and stern blocks.

Allow the fiberglass resin to partially set, then using an Exacto knife cut away any excess fiberglass cloth that has extended into the penetrable areas of the ship. After cutting, smooth the cloth down again along the cut edge using a gloved hand. Wetting the resin with water first to provide some lubrication helps to keep the resin smooth. As soon as the resin on the bottom of the hull is set enough (but not fully cured) invert the hull and apply cloth and glass to the top of the bow stern and cap rail, overlapping the sides of the caprail down to the penetrable area. When you are through the entire outside of the hull will be covered with fiberglass cloth and resin except for the penetrable areas. Once the resin begins to set up trim away any cloth that extended into the penetrable areas and smooth down the cloth. Remember no wrinkles or air bubbles should be allowed in the cloth. Now invert the hull and sit it back on the wooden block upside down.

Apply another layer of glass cloth and resin down the center of the hull bottom from bow to stern. This sheet does not need to extend up the side of the hull to the penetrable area, but just cover the flat part of the hull bottom to provide more reinforcing in the base plate to strengthen the butt joints that were glued together.

At this point you may want to install optional frames to butt your balsa sheeting up against. Some people like these since they create a “window frame” that you cut the balsa to fit into. The advantage is that all the work in tapering the balsa sheet to the hull profile is done once with the frame the disadvantage is that when you install the balsa it has to be cut to fit this frame. If you decide to add this frame you’ll need to get some wood stringers that are 14″ wide and the thickness of your balsa sheeting. Glue these 1.25″ below the waterline (this gives a 1/4″ of hull for you balsa to glue on to) and 1/4″ fore and aft of the penetrable areas. Use automotive putty to taper the edge of the framing to the ship’s hull. Let dry and sand. You may need to apply a few layers to get it smooth.

Brush another thin coat of resin over the entire hull and caprail. As this coat of resin sets make sure the job “looks right.”  Look for thin spots in the resin. If it looks good and you are happy with it then let the hull dry completely. Otherwise, apply another thin coat of resin. If there are a few “rough” areas it won’t make all that much difference and they will be corrected later. On a warm day this could take only a few hours for the resin to cure, other times it can take several days for all “tackiness” to vanish. Again the two part resins are tricky things to mix and the solar cured resin is preferred although use of an old mirror might be required to get the sun to all parts of the hull for complete curing.

Once the fiberglass resin has set completely sand lightly with fine grit (150) sandpaper on a sanding block or orbital sander. Sand lightly is a key word. You do not want to sand through the resin and into the cloth anywhere! After the sanding is complete wipe off the hull with a damp cloth then skim on a coat of automotive putty over the entire hull surface that was fiber glassed. A plastic putty knife works well to skim on the filler, allowing the filler to fill in only low spots and to smooth out rough areas. I recommend the automotive filler putty because it is easy to work with, is waterproof, and is easy to sand. Once it dries sand the hull again. You may have to repeat this procedure to get a really smooth finish, especially in the areas where the glass cloth was overlapped.

Now all you need to do is to skin the ship by gluing the appropriate thickness of balsa wood sheeting.

Click each image to enlarge. We apologize, but this is the best resolution we have for these images.

(Original Article by Phil Sensibaugh, edited by Bill Pickl and Strike Models) Note: this is one section of a comprehensive model warship construction manual originally published on the BDE/RC website. This section is applicable to both Big Gun and Fast Gun combat.

First things first – decide what ship you want to build.
This decision alone may take many months of procrastination while sorting out all the facts that seem pertinent when in reality, it doesn’t make all that much difference. I have participated in about 50 RC combat warship battles over the past five years and have followed the action of other clubs closely. One thing that I have learned is generally, there is no such thing as a bad boat. Assuming a boat is reliable and well balanced so it is seaworthy, and put in the hands of a skipper that has learned how to use the features of the particular ship to his advantage any ship can be an effective part of a team.

Ask yourself why you want to participate in this hobby.
Presumably the reason is to occupy free time and consume some disposable cash, for this hobby will certainly do that, but more likely the real reason is to have fun. The best way to have fun is to have a ship that is reliable and seaworthy. It’s very frustrating to have your ship role over and sink as soon as it begins to take on water, or to spend the day sitting at the side of the pond working on your ship instead of participating in the game.

Consider a used ship as your first ship.
This will allow you to begin playing the game sooner and there is no better way to decide what ship fits your style than to participate in the game for awhile in order to learn your strengths and weaknesses. If you go this route, you want to see the ship in person and in action — there are too many sad stories of buying a ship sight-unseen and not having it be as represented (broken, inoperable, rotted, rusted, etc.). Ideally the owner will allow you to battle the ship before you purchase it and to have an experienced third party examine the ship. If you like how it responds to your style of battling and it operates reliably through the day it is a good choice to get you in the game quickly. When you get a ship test all systems to ensure that they work, and how they work, then use this ship to gain combat experience and as a construction aid and test bed for your new ideas. That’s right. To test out your new ideas. About every modeler I have ever known has his or her own ways of accomplishing tasks and you will find yourself asking, “Why did the original builder do it this way?” Most often there was a reason, but sometimes it was just a mistake, an attempt to implement a new idea that didn’t work very well. There is no substitute for experience in building a ship and learning combat techniques.

Avoid small ships and complex ships for your first building experience.
There are many operational systems in our warships and every system is equally important in its own right. Think about it, which is more important, cannon, drive motors, pump, steering, or balance? After a little reflection you will probably decide that all systems are equally important since your ship won’t be combat effective if any of these systems don’t work well. It’s by far and away easier to learn the basics of maintenance and installation on a ship that has fewer operational systems. It is easier to get the hardware installed in a larger ship. Small ships test the talents of the most skilled builder. For your first ship you will be well advised to build a larger ship rather than a smaller one. Larger ships are more survivable in combat as well.

Keep it simple.
Another sound tidbit of advice would be  don’t try to reinvent the wheel. Stick to the basic and proven methods of implementing a function. Look at the ships of the seasoned skippers and pay attention to how they implement the various functions, then follow suit.

This manual is a collection of articles that originally appeared on the BDE/RC website as a how to manual for building Big Gun RC model warships. Strike Models has made some edits and updates to the documentation, and incorporated Fast Gun information when available. However, the original articles are now several years old, and construction methods and rules may have changed since they were written. Please check with your local club or one of the resources listed in the links section before taking this information as gospel.

Table of Contents

Getting Started and Choosing a Ship

Scratch Building a Model Warship

Water Channel Construction


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One of the things we have heard people having problems getting the interuptor pin set correctly after disassembling the cannon for cleaning or maintenance. While I am not an expert on this yet, I have found this method of setting the interruptor cap to be fast and effective. This process has to be done without an o-ring at the base of the barrel (and will not work at all with a geek breach).

1.  Screw the interruptor cap all the way in (without pinching the pin itself).
2. Fill the magazine with BBs and cap the magazine.
3. Position the cannon as shown in the picture.
4. Slowly unscrew the interruptor cap.
5. As some point, a number of BBs will fall out.
6. Further unscrew the cap by 1/8 turn. The position is now at least very close.
7. Test the guns in this configuration to make sure a single shot is fired each time (adjust as needed)
8. Secure the cap with Loctite (blue is preferable) to keep the adjustment stable.
9. Test one last time before the Loctite sets.

Holding the cannon in this position allows several BBs to drop as soon as the interruptor pin is withdrawn enough.

In order to make our ships penetrable, we need to cut large windows in the fiberglass hulls. For those who have not done so before, cutting the hulls can be practically traumatic. Here are some tips on how to make the cutting much easier. These instructions assume that the hull has already been marked for cutting (our 3/8 inch tape works well for this) and has had the corners drilled.

For a long time, the tool of choice for cutting the windows in our fiberglass hulls has been the Dremel rotary tool with a fiberglass reinforced cut-off wheel. These wheels wear quickly, but they work. The standard ceramic cut-off wheels are not suitable for cutting hulls as any misalignment in the cutting will cause the wheel to shatter. Within the last couple of years, we found that the carbide cutting/shaping wheel (#543) works better than either of these wheels for cutting the windows in the hulls. I’ve only purchased a single one of these wheels and cut many hulls with it. The wheel base is metal, so the chances of the wheel breaking are very slim, and they do not wear out quickly.

Very recently, I found a tool that I think works much better than the Dremel rotary tool for cutting the hulls. This tool is one of the oscillating tools such as the Dremel Multi-Max combined with the grout removal blade or the Harbor Freight Multifunction Power Tool combined with a carbide half moon blade (HF #67462). With the HF tool and carbide blade, I cut out one half of the HMS Hood in one 35 minute session (and it was the first time I had used the tool). I timed myself at starting a 3 inch cut every 15 seconds. What I liked about using the tool is that you never felt like you were straining to keep the cutting action under control like one would with a rotary tool. You also only need to apply a little pressure to the tool against the fiberglass instead of forcing the blade along the cut. I did best by rolling the blade slowly between the drilled corners to cut through the gel coat, and then rolled the blade back to cut through the fiberglass below. One other thing I really like about this type of tool is that it doesn’t throw the fiberglass dust around like the rotary tools do. You still need to be wearing goggles and breathing protection, but the dust is much better. On the negative side, your hand will get tingly from holding the vibrating tool.

I’ve also tried the Harbor Freight inexpensive diamond wheel, but the this wheel takes three times as long as the carbide one. A more expensive diamond cutter might work better, but I haven’t picked one up.

After cutting the windows in the hull, you will almost certainly find that parts of the window panes and caprail will be too thick. Once again, Harbor Freight comes to the rescue. They have a finger width hand held belt sander that makes very short work of the sections that are too thick. The entire hull can be fixed in only minutes, depending upon now close the original cut was.



After about eight months of use, my Harbor Freight Multifuction Power Tool died. One of the motor brush springs broke. I’d found that I almost completely stopped using the Dremel rotary tool except for some metal cut-off and polishing during this time. With the death of the HF version, I’m keeping to my rules about buying cheap tools (buy a cheap tool once; if it breaks, you’re using it enough to warrant getting an expensive one). The Dremel Multi-Max is a much nicer tool for our purposes. The ability to change oscillation speeds is nice, but the really nice thing is that it is half the weight of the HF version. This makes it much easier for one handed usage, which is typically needed when cutting hulls.